The doctoral dissertation in the field of Biology will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus and online.
What is the topic of your doctoral research? Why is it important to study the topic?
The endangered Saimaa ringed seal (Pusa hispida saimensis) inhabits the labyrinthine Lake Saimaa in Eastern Finland. Highly susceptible to changes in its habitat, a thorough understanding of its behavioural ecology is crucial for implementing targeted conservation measures. In my doctoral thesis, I explore key aspects of the seal behaviour during the moulting season, including spatial, temporal and social fidelity patterns.
First, I explored fidelity to moulting sites. This part of my research investigates whether seals tend to return to the same locations each year and whether such preferences differ across lake basins or between sexes. Second, I focused on the timing of the moult. The moult coincides with the complete disappearance of the ice covering the lake, a significant environmental shift. I examined how factors such as temperature, daylight hours and ice cover affect the timing of the moult.
Finally, I examined the sociality of the seal. While the Saimaa ringed seal is generally solitary, some individuals are observed moulting together in pairs or small groups (up to five seals). My research investigates the factors driving these social groupings, such as habitat availability, site fidelity, and sex. It also explores whether these groupings form long-term companionships.
What are the key findings or observations of your doctoral research?
This thesis complements decades of research on the endangered population of ringed seal inhabiting Lake Saimaa. It provides additional insights into the behavioural ecology of the seal, highlighting the importance of the labyrinthine nature of the lake and environmental conditions in shaping spatial, temporal and social fidelity patterns during the moult. I confirmed the earlier evidence that Saimaa ringed seal individuals display a high degree of moulting site fidelity.
However, the unprecedent scale of my research found that each individual seal has only a handful of locations, separated by a few hundred meters. Interestingly, females showed more variation in their distances between successive moulting sites than did males, suggesting an effect of post-nursing behaviour on their choice of moulting locations. I then showed that the amount of daylight was the main environmental variable controlling the moult, and that the moulting peak is occurring around the 18th-20th of May. I also found that both ice thickness and air temperature had an effect of female moulting phenology, but not on males. These further imply that female nursing investment and success play a role in their moulting behaviour.
Finally, I found that, despite their solitary nature, Saimaa ringed seals display some degree of sociality during their moult, likely the results of habitat availability and moulting site fidelity. The majority of the identified seal pairs consisted of a male and a female, potentially representing mating pairs. I further observed the existence of long-term companionship, suggesting the existence of more complex factors driving the sociality of the seal that are yet to be discovered. My study is the first to report individual associations among ringed seal and one of the rare examples describing sociality in a non-colonial seal species.
How can the results of your doctoral research be utilised in practice?
The present work not only describes interesting behaviour during the moult, but also provides valuable knowledge for the conservation of the Saimaa ringed seal. For instance, the strong moulting site fidelity should be considered in land use planning. Recreational development (e.g., summer cabins), particularly in the vicinity of moulting areas, could have a significant impact on the seals.
Additionally, seal watching is an increasing activity around Lake Saimaa and happens almost exclusively during the moult when the seals are hauled out and easily observable. My results on moulting site fidelity and temporal fidelity could be used to write guidelines for companies offering seal-watching tours, ensuring the sustainable development of their practices. They may, for instance, legislate on the minimum distance for observation, the daily and seasonal frequency of visits to moulting sites, or the intensity of the activity.
Finally, although climate change will primarily impact the breeding of the Saimaa ringed seal, the earlier disappearance of the ice habitat is likely to also affect its moult. The habitat transition may shift in time, with ice no longer present at the beginning of the moulting season, forcing the seal to rely solely on rock platforms. Additionally, the loss of ice habitat, which plays a significant role in shaping seal sociality, will likely disrupt grouping patterns. Our work provides a baseline for future research on spatial, temporal, and social patterns of the Saimaa ringed seal in response to these environmental changes.
What are the key research methods and materials used in your doctoral research?
The work presented in this thesis is based on the extensive photo-identification (Photo-ID) dataset of the Saimaa ringed seal, which was created and is maintained by the Saimaa Ringed Seal Research Group at the University of Eastern Finland. Ringed seals derive their name from the distinctive rings that mark their pelage. Each seal has a unique and permanent combination of rings, which we used to identify individuals. This non-invasive identification method, implemented in 2010, has led to the documentation of over 570 individuals (some of which have since died) from more than 6,400 seal sightings and hundreds of thousands of photographs. The Photo-ID program is a collaborative effort between the University of Eastern Finland and Metsähallitus. It is also a citizen science project, involving over twenty volunteer photographers and members of the public who contribute seal pictures.
This extensive data collection has been financially supported by various agencies and non-governmental organisations over the years, with current funding from WWF Finland and the EU LIFE Programme (Our Saimaa Seal LIFE). I extracted several metrics from this dataset (e.g., successive distances to moulting sites, daily seal counts, number of associates) to explore the spatial, temporal and social fidelity patterns of the seal during the moult. I then applied various ecological modelling approaches, including Generalised Linear Mixed Model, Generalised Additive Mixed Model, and Social Network Analysis.
The doctoral dissertation of Vincent Biard, MSc, entitled Moulting behaviour of the Saimaa ringed seal: Exploration of socio-spatio-temporal fidelity patterns will be examined at the Faculty of Science, Forestry and Technology, Joensuu Campus. The opponent will be Professor Toni Laaksonen, University of Turku, and the custos will be Docent, Senior Researcher Mervi Kunnasranta, University of Eastern Finland. Language of the public defence is English.
For further information, please contact:
Vincent Biard, vincent.biard@uef.fi, tel. +358 50 304 4153
